In our recent work, We demonstrate a simple and scalable approach to increase conversion efficiencies of nonlinear metasurfaces by incorporating them into multipass cells and by letting the pump beam interact with the metasurfaces multiple times. We measure an order of magnitude enhancement in the SHG signal when the incident pump traverses the metasurface up to nine passes. For more details, check our publication in ACS Photonics here.
Our recent work on 'Phase-Matched Second-Harmonic Generation from Metasurfaces Inside Multipass Cells' is now on ACS Photonics
